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Title: ABSORPTION AND TRANSLOCATION OF GLYPHOSATE ISOPROPYLAMINE AND TRIMETHYLSULFONIUM SALTS IN ABUTILON THEOPHRASTI AND SETARIA FABERI

Author
item SATCHIVI, NORBERT - UNIV OF ILLINOIS
item WAX, LOYD
item STOLLER, EDWARD - RETIRED USDA EMPLOYEE
item BRISKIN, DONALD - UNIV OF ILLINOIS

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: We planned and conducted growth chamber and laboratory experiments to determine if there was any difference in uptake, translocation and effectiveness of two different salts of glyphosate using two weed species. Glyphosate was applied as the isopropylamine (IPA) or the trimethylsulfonium (TMS) salts using both unlabeled and radiolabeled formulations. Absorption of both formulations increased over the 72 hour time period of the study. After 72 hours, velvetleaf absorbed 26% of the herbicide, regardless of formulation, while giant foxtail absorbed 43% of the herbicide with both formulations. We found that the addition of ammonium sulfate (AMS) to the spray solution increased absorption of both of the formulations equally. Translocation of radiolabeled herbicide throughout the plants was the same for both formulations. For velvetleaf, a majority of the herbicide moved to tissue above the treated leaf, whereas for giant foxtail, a majority of the herbicide moved to tissue below the treated leaf. These results indicate that uptake, translocation and effectiveness of glyphosate on two unrelated important weed species were equal for the IPA and the TMS formulations of glyphosate. These findings are important and useful to researchers and outreach personnel in the public and private sector who are planning and conducting research and writing guidelines and recommendations for use of the various formulations of glyphosate for weed management in crop and non-crop situations.

Technical Abstract: Growth chamber and laboratory experiments were conducted to evaluate foliar absorption and translocation of isopropylamine (Ipa) or trimethylsufonium (Tms) salts glyphosate in A. theophrasti and S. faberi. Glyphosate was applied at 250 g ai ha-1. Absorption of 14C-glyphosate in both formulations increased similarly in both species over 72 h. Seventy-two h after treatment (HAT), A. theophrasti absorbed 26% of applied 14C of both formulations, while S. faberi absorbed 43% of both formulations. The addition of 1% ammonium sulfate (AMS) to both formulations increased the amount of herbicide absorbed to 35% in A. theophrasti and 60% in S. faberi 72 HAT. At 72 HAT, translocation of absorbed 14C-glyphosate in both formulations (with or without AMS) was greater for S. faberi than A. theophrasti. For A. theophrasti, 17% of absorbed Ipa or Tms were translocated out of the treated leaf, while additions of AMS increased the amount translocated to 25 and 23% for Ipa and Tms, respectively. The largest portion of translocated 14C moved to tissues above the treated leaf. For S. faberi, 37% of absorbed 14C in both Ipa and Tms formulations were translocated out of the treated leaf 72 HAT, while 42% translocated when 1% AMS was added to both formulations. In S. faberi, the largest portion of 14C-glyphosate translocated to tissues below the treated leaf. Overall, in both weed species no differences were found between Ipa and Tms formulations.